Stationary directional solidification followed by heat treatment of a Cu-Al-Ni-Mn SMA

Cu-based shape memory alloys (SMA) present a good shape memory effect (SME), good thermal stability and high transformation temperatures. To produce these alloys a rapid cooling is necessary in order to avoid the formation of equilibrium phases and obtain the metastable phase, which is responsible for the SME. An alternative route for this procedure is to perform slow solidification followed by isothermal heat treatments and quenching. The aim of this work is produce an ingot of Cu-11.8Al-3.2Ni-3Mn (% wt.) SMA casting by stationary directional solidification followed by heat treatment, with a view to investigate the microstructural evolution, as well as the thermal and mechanical properties. The samples are characterized by X-ray diffraction (XRD), optical microscopy (OM), differential scanning calorimetry (DSC) and Vickers microhardness. Directional solidification has not been able to produce the metastable phase responsible for the SME, which are formed only after heat treatments. (author)